Accumulator



Ma 27, 1947. B, UNTON 2,421,076

ACCUMULATOR Filed Sept. 4, 1942 FIG. a

- INVENTOR. THOMAS B. LINTON AT ORNEY Patented May 27, 1947 ACCUMULATORThomas B. Linton, North Hollywood, Calif., assignor, by mesneassignments, to Bendix Aviation Corporation, South Bend, Ind., acorporation of Delaware Application September 4, 1942, Serial No.457,372

4 Claims.

l This invention relates to hydraulic-pneumatic accumulators of thebladder type for use in hydraulic systems, for example in the hydraulicsystems of airplanes.

Accumulators are used for storing hydraulic fluid under pressure. Ingeneral, they comprise a shell having an air connection and an hydraulicconnection with a flexible partition between the air and hydraulic fluidso that the hydraulic fluid may act against the air without possibilityof contamination by the air. The hydraulic fluid acts against thecompressed air so that pressure will be maintained in the storedhydraulic fluid. It has been found that accumulators of the bladder typecan be made lighter than accumulators of the diaphragm type, and it iswith bladder type accumulators that this invention is concerned.

One of the tests to which all accumulators must be subjected is theapplication of a hydraulic test pressure which is usually double ortriple the system pressure, when all air is removed from theaccumulator. In such tests the bladder completely collapses, foldingback upon itself and being pressed against the air inlet. To prevent thebladder from being extruded into the air inlet, and thereby damaged,metal discs are inserted in the bladder to, bridge or cover the airinlet hole. Therefore, means must be provided to center the metal discsupon collapse of the bladder so that they will fit over the air inlet.Also, means should be provided to cause a radius of bend in the bladderat the point where it folds back upon itself, inasmuch as the syntheticrubber material of the bladder becomes extremely brittle at very low,test temperatures and may crack if a sharp bend is imposed upon it.

The present invention satisfies both of these requirements, and ingeneral comprises an internal bead Within a bladder which causes a thicklocalized section which retains its position during deflation of thebladder, causing the bladder to fold about the bead to provide a radiusof bend, and at the same time centering the metal discs to cover the airinlet.

It is therefore an object of the invention to provide an accumulatorwith a bladder which will center metal discs over the air inlet of theaccumulator.

It is another object of the invention to provide an accumulator bladderhaving means to create 2 a radius of bend at the point where the bladderis folded upon deflation.

Still another object is to provide an accumulator bladder which willsimultaneously provide a radius of bend for the bladder material andalso center metal discs with respect to an air inlet.

In the drawings forming a part of this specification:

Figure l is an elevation view, in full section, of an accumulator of thetype embodying the present invention; and

Figure 2 is an elevation view, in full section, of a bladder ofelongated shape embodying the invention.

Referring to Figure 1, a shell Ill has welded to the bottom thereof athreaded hydraulic fitting l2 through which hydraulic fluid enters andleaves the accumulator. Welded to the upper end of shell I0 is a collarM which is internally threaded at 16 and provided with a shoulder l8 andan inwardly projecting lip 20. Fitted within shell I0 is a bladder 22having a preformed shape substantially like the interior of shell l0.Formed on the upper end of bladder 22 is an outwardly projecting lip 24which hooks over the inwardly projecting lip 20 of collar 14. At aboutthe midsection of bladder 22 there is provided an internal bead 26 whichforms the subject matter of the invention. Secured to the bottom ofbladder 22 is a lower disc 28 and an upper disc 30 held together by ascrew 32. Lower disc 28 fits over hydraulic outlet I2 when the bladderis fully extended as shown in full lines, and upper disc 30 fits overthe air inlet as shown in dotted lines.

Placed within collar I4 is a plug member 34 which fits snugly againstthe upper end of bladder 22 and holds bladder lip 24 in contact withcollar lip 20. An annular nut 36 is threaded into collar M to hold plug34 in place. A cotter pin 38 passes through collar l4 and fits in a slotill in nut 36 to lock nut 36 in position. Plug 34 has a central hole 42therethrough into which is threaded an air valve element 44.

In operation, air is inserted into the accumulator through valve element44 and the bladder assumes the general shape as shown in full lines.There it will be noted that lower disc 28 bridges the opening ofhydraulic outlet l2, so that the air pressure will not force the bladderinto outlet I2 and damage the bladder by extrusion.

Outlet I2 is then connected to a hydraulic system including a pump, andhydraulic fluid under pressure enters the accumulator forcing thebladder 22 upwardly until the air is compressed to a pressure equal tothe hydraulic pressure. Thereafter hydraulic fluid will be added to orsubtracted from the accumulator according to the de mands of thehydraulic system and the pressure available from the pump of thehydraulic system.

When it is desired to test the accumulator, the air valve 44 is openedallowing all air to escape from the inside of the bladder 22. Hydraulicfluid under pressure is then pumped in through fitting l 2 and thebladder gradually collapses, the thin lower half of the bladderprojecting upwardly into the thicker upper half of the bladder, whichmaintains its position against the shell l because of its thickersection. The bead 26 guides the lower half evenly into the upper half ofthe bladder because it is a thickened portion which will resistdeformation to a relatively greater extent than the thinner wall of thelower half. Thefinal state is that shown in broken lines in Figure 1,wherein the lower half of the bladder is pressed tightly against theupper half,

and the disc 30 is centered over hole 42. It will be noted from anexamination of these broken lines that'there is an appreciable radius tothe bend about bead 26. This radius is very important in preserving thebladder because at a low temperature such as 50 R, which may beencountered in actual use, the bladder material becomes somewhat brittleand often cracks if folded fiat upon itself without a radius beingprovided for the bend.

Shown in Figure 2 is an application of the invention to an elongatedbladder 60, which has an upper bead 62 at about the mid-point of thebladder 60 and a lower head 64 below head 62. As the bladder 60collapses the lower bead 64 will center the lower part of the bladder inits deflation 50 that it will not strike against one wall of the otherfirst and be deflated thereafter by a dragging or rubbing motion againstthe wall which it touches. Upon further deflation, the bead 64 will curlinternally with the rest of the bladder and the bead 62 then tends tocenter the bladder upon complete deflation, providing a radius of bendas well as centering any disc which may be inserted in the bladder.Figure 2 therefore shows an application of the invention to provide forprogressive collapse of the lower part of a bladder such as isaccomplished in Figure 1 by thinning the lower wall.

Referring to Figure 1, the bead 26 should be placed midway in thebladder as determined by completely inverting the lower half of thebladder into the upper half as assembled. so that the head will alwaysbe at the radius of bend of the bladder. The shape of the bead isimportant and is preferably an abrupt projection on the lower side and agentle projection on the upper side, so as to ease the radius of bend tothe greatest extent. This desired shape is limited. however, by thecomplications of molding the bladder 22 and the theoretical shape may beimpracticable from the manufacturing standpoint. The shape shown,however, is satisfactory.

The invention has been described with reference to particularembodiments thereof. but it is not intended, however, to limit theinvention to these embodiments nor otherwise except by the terms of thefollowing claims.

I claim:

1. An accumulator bladder comprising a bladder of flexible material, anda plurality of transverse annular thickened sections in said bladder tocentralize said bladder as it collapses to prevent rubbing of thematerial and to provide a head of material about which the fold occurswith an appreciable radius of bend for folds in the material.

2. An accumulator comprising a shell having an air opening and ahydraulic opening, a flexible bladder secured therein and separatingsaid air opening from said hydraulic opening, said bladder having aportion conforming to the shape of said shell and having another portionadapted to telescope into said conforming portion, and an inwardlyprojecting head on said bladder substantially at the line of junction ofthe two bladder portions, said head forming a pad of material aboutwhich the bladder folds with an appreciable radius of bend when theportions completely telescope.

3. An accumulator comprising a shell having an air opening and ahydraulic opening. a flexible bladder secured therein and separatingsaid air opening from said hydraulic opening, said bladder having athickened portion normally conforming to the shell, and a thinnerportion adapted to telescope into said thickened portion. said thickenedportion terminating abruptly forming a termination line which allows thethinner portion to fold with an appreciable radius of bend when theportions are telescoped.

4. An accumulator comprising a shell having an air opening and ahydraulic opening. a flexible bladder secured therein and separatingsaid air opening from said hydrau ic opening. said bladder having aortion conforming o the shape of said shell a d having another port nada ted to telescope into said conformi g portion. and an inw rd yrojecting head on said b adder substantia lv at the l ne of junction oft e two b adder portions, said head being smoot ly curved and forming apad of material about which t e b adder folds with an appreciable rad usof bend hen the portions completely telesco e and the bead being of suchcross-sectional s ape that t e angle between said other nortion of saidbladder and the side of said bead adjacent thereto is less t an theangle between the first-mentioned or on and the other s de of the beadwhen the bladder is fully distended.

THOMAS B. LINTON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,256,835 Mercier Sept. 23. 19411,301.354 Baird Apr. 22. 1919 841.791 Lemp Jan. 22, 1907 2.105.160Pequerez Jan. 11, 1938 2,299,611 Clark Oct. 20. 1942 Re. 20.887 MercierOct. 18. 1938 2,246,621 Davis June 24, 1941 FOREIGN PATENTS NumberCountry Date 5.796 Great Britain May 12, 1885 53,868 Denmark Apr. '17,1934

